Veneering elastomers



Patented Mar. 16, 1948 VENEERING ELASTOMERS Elden Earl Leach, Jr.,

to E. I. du Pont de N mlngton, Del., :1. corp This invention relates toa process for veneering elastomers and particularly for veneeringelastomers with different elastomers having different properties and tothe resulting products.

It is well known to veneer an elastomer with a different elastomerhaving different properties so as to obtain an article with the bodyportion formed of an elastomer having certain desirable properties and asurface having different desired properties. The most common method ofcarrying out such operation in commercial practice has been to pass theveneeringelastomer between rolls to give it a desired thickness whichmust be above 0.03 inch, then placing it upon the base stock, moldingthe composite product and then vulcanizing the two together. Thisprocedure has not proved to be satisfactory for several reasons. Theveneering elastomers must have a thickness above 0.03 inch in order thatthey can be handled. Due to the cost of the veneering elastomer, this isuneconomical and has greatly restricted the practical use of suchprocedure. This procedure is diificult to carry out and requiresconsiderable time and labor which is also objectionable because of thecost and the time element. Further, when such composite materials aremolded, particularly in odd shaped and intricate molds, the basematerial is extended thinning out the veneer in the extended portions sothat the .veneer is not of uniform thickness throughout the finalproduct and, in some cases, the extension may be so great that the baseportion will break through the veneer and become exposed in the moreextended portions. Still further, when the elastomer is caused to flowin a mold, it often binds and adheres to the surface of the moldcreating a rough surface in the finished article.

Another method of applying a veneer to a base stock has been to make asolution or a, dispersion of the veneering elastomer, apply the solutionor dispersion to the base stock by painting, spraying or the like,allowing the solvent or dispersing medium to evaporate, then molding andvulcanizing the resulting composite article. This procedure also has thedisadvantage of causing the veneer to thin out during the molding sothat the final product does not have a uniform thickness of veneer.Also, this procedure tends to produce articles with rough surfaces dueto binding and adherence of the elastomer to the mold during the moldingstep. Further, in this procedure, the solvents and dispersing mediaevaporate very slowly and the composite material is sticky and difiicultto handle. Y

Norristown, Pa., assignor emours & Company, Wiloration of DelawareApplication October 20, 1942, Serial No. 462,755 A 12 Claims. (01.18-59) It is an object of this invention to provide a new and improvedmethod for veneering an elastomer composition with a different elastomercomposition having difierent properties. Another object is to providesuch a method wherein the veneer is of uniformthickness and whereinveneers may be obtained which will be thinner than can be obtained bythe laminating process. A further object is to provide such a methodwhich can be carried out more readily in a shorter period of time andmore economically. Still another object is to provide such a methodwhich will provide articles of more perfectly smooth surfaces. A stillfurther object is to provide new articles of manufacture comprising abody portion of avulcanized elastomer composition having a uniformcoating of a different vulcanized elastomer composition. Other objectsare to advance the art. Still other objects will appear hereinafter.

The above and other objects may be accomplished in accordance with myinvention which comprises coating the molding surface of a mold with avulcanizable veneering elastomer composition dissolved or dispersed inan inert volatile liquid, drying the coating, placing in the coated molda mass of a different vulcanizable elastomer composition, applyingpressure to force such mass to conform to the mold and then vulcanizingthe composition in the mold by subjecting them to vulcanizingtemperatures. Upon stripping the resulting composite product from themold,'it will be found that the coating of veneering elastomer is firmlybonded to the surface of the base stock and will be of substantially thesame thickness as the coating originally placed on the surfaces of themold. This could not have been predicted since the molding of the basestock caused it to flow and, due to the friction of the surfaces of thebase stock in contact with the surface of the film of veneer, a severedrag is placed on the film of veneer. However, the film of the veneeradheres to the surface of the mold with sufiicient tenacity so that suchdrag does not substantially affect the thickness of the film.

The term elastomer as employed herein and in the claims means an elasticrubber-like substance including natural rubber as well as syntheticrubber-like products. The term elastoprene as employed herein and in theclaims is used to designate natural rubber and synthetic rubber-likeproducts derived from butadienes, isoprenes and the like. The termelastothiomers is employed herein andin the claims to designate thepolyalkylene sulfides such as are p Nomenclature of synthetic rubbers,appearing;

Rubber Chemistry and and are employedin pages 900 to 907'of Technology,vol. 12 (1939), herein with the same meaning asgiven-to them by H. L.Fisher in such article,

My invention will be more readily understoodg from the detaileddescription, hereinaite given,

when taken with the accompanying drawing in The bo e m usually beemployed as temperatures of the veneering elastomer composition. Suchsolvents include volatile aromatic and aliphatic liquids and water, suchas xylene, toluene, methyl ethyl ketone, methanol, ethanol, water,ethylene dichloride and the like. The particular liquid employed willdepend upon the veneering elastomer composition and the one, which isknown to be most suitable for the particular composition, will be theone usually employed. For example, ethylene dichloride Will the liquidmedium for veneering compositions in which the elastomers which 2represents the lower portion of amold having depressions 4 thereinoutlining a suitable design. The upper portion 6 of the mold isprovidedwith ashaftfi through which pressure may be applied to forcea, massltoflow. and conformv to thecontoursofthe mold. The. two portionsof-themold,m aybefastened together by bolts l0 and nuts l2.

In carrying out my invention,- a solution or dispersion of the.veneering, elastomer in .a volatile liquid is applied .totheinnersurfaces of the mold and then dried to, form a uniform coating ofthe veneering'. elastomer IL on the surfaces of the mold. Then a. mass.of --a,different yulcanizable elastomer.

medium, may be used as ;a veneering.material for veneennga .basgstockwhich will be a different, vulcanizable. elastomer composition in whichthe. elastomer maybe the same or different from the elastomer in theveneeringcomppsition, Usually,

the base stock will-comprise a relatively cheap elastomer composition,such as natural rubber, which doesnot have the physical properties desired for the surface of the article and the veneer ing article.However, this is not essential as the base stock-.may be vcomposedof anelastomer having certain desirable characteristics, such as, resistance:o: re zi nda neer e: l s me composition may have other desirablecharacteristics, such as,resista nce to the action of solvents; Apreferredcomposite article will com-, stock with a. Another pre-.

prise a rubber; composition; base; coating of a chloroprenekpolymfir.

l6, is;placed .in the mold and the two parts of-the mold forced: towardeach other so as.

elastomercomposition will generally be a more expensive elastomercomposition which willhave theproperties desired forthesurface. of-theferredvarticle is one inwhich the base stock is a freeze resistantchloroprene polymer composition coated with a solvent-resistantelastomer compo sition, such asfThiokoLF which is believed to beapolyalkylene polysulfide, obtained by the reaction oi-an alkali metalpolysulfide on an alkylene dichloride. V

The liquid, in which is dissolved or dispersed, should be one which ischemicallyinert, thatis, which does not react with-the ingredientsof-Qthe elastomer composition.

and onewhich issufiiciently. volatile so .that'it can be readily removedfrom the coating-on the mold by evaporation at the usual vulcanizingheveneering composition arethe polyalkylenesulfides.

V l 91 1113i on; or dispersion of the vulcanizable veneeringelastomercomposition may be applied to the mold byspraying, painting, dipping orany other feasible means for uniformly coating the moldywith suchmaterial. The liquid carrying medium will also be chosen with regard tothe method .to be employed for applying the material to, the. mold.Usually, when the sprayingmethod-is to. be, employed, the boiling pointof the liquid should be around 290 F. or above, since liquids ofmaterially. lower boiling point will tend to cause whipping. of thesprayed solutions and hencewill-usually be unsatisfactory for spraying.I have, found xylene, tobe ,a particularly satisfactoryliquid medium,especially for chloroprene polymer compositions, as it has .a boilingpoint of 291 F., which issufficiently high to make it suitableforspraying and yet which is sufiiciently low to permit evaporation from=ahot mold. Compositions, in which xyleneis employed as the carryingliquid, will .dry. out in a proximately30 seconds at amold-temperatureof about260' F, to.

painting, dippingand-other methods of applying the coatingto themold.Other liquids, havinglower boilingpoints andhigherevaporation rates,may-also be .employed when the solution ordispersion isto -be painted onthemold or applied thereto in some similar manner and such compositionswill naturally d y out at a more rapid rate,

The thickness o f the. veneer will be predeterminedby the operator atthe time of coating'the mold with theyeneering composition, It willusually-be desirable-to have the mold hot, at the t me of a n he enc r ap t on-as a more uniform coating will thereby beobtained andthe, coatingWilldry out; more rapidly. By ot-7 m ibatthe e nhou e ea o a temperatureapproachin the normal vulcaniz ing temperature of the vulcanizableveneering composition. A qll i ck;;covering of the-mold by spraying orpainting. will usuallyjcrm a coating 1 of;theyeneeripgcomposition with athickness of from;'about 0;001. inch;toabout 0.005 inch. By repeatingthe; coating operation; films ,of veneer ing; eomposition may bebuiltupto any desired thickness. Usually, coatingshaving a thickness up toabout 0.020'inch'can be obtained before, the mold temperature becomestoo low to cause the eflicient evaporation of -liquid. Thicker coatingsmay be. obtainedby, heating the mold to maintain its, temperature duringthe application of the coatings.

However, it wouldv generally be undesirable to form a veneer having athickness above 0.050 inch. For most purposes, a veneer having athickness of from 0.001 inch to 0.020 inch will be quite satisfactory.Generally, I prefer to provide a veneer having a thickness of from 0.001inch to 0.005 inch. For example, a veneer of a chloroprene polymer,having a thickness of about 0.005 inch on an automobile tire sidewall,has proved to be very satisfactory in protecting the tire from theaction of ozone and from abrasion and cracking.

In some commercial adaptations of my process, it may be found desirableto lubricate the mold with any of the commonly employed mold lubricantsprior to applying the solution or dispersion of the veneeringcomposition. However, my experience has indicated that such lubricationis usually not necessary. If lubrication is used in any case, the amountshould be very carefully controlled in order to avoid wiping off of theveneering composition during molding.

In order to more clearly illustrate my invention, the preferred modes ofcarrying the same into effect and the advantageous results to beobtained thereby, the following examples are given:

EXAMPLE I A .chloroprene polymer was compounded to improve its attritionand aging properties and put into solution by means of xylene. Thefollowing formula was used in preliminary experiments and has been foundto be satisfactory:

A semi-fluid polymer of chloroprene, prepared substantially according toExample 51 of U, S. Patent 2,234,215 100.00 Piperidinium pentamethylenedithio-carbamate 1.0 Barium sulfate 45.0 Titanium dioxide 8.0 Zinc oxide5.0 Xylene 300.0

Smoked sheets 100.0 Zinc oxide 5.0 Carbon black 25.0 Stearic acid 2.0

Butyraldehyde-aniline condensation product 1.0 Sulfur 3.0

The chloroprene film adhered tenaciously to the mold during this shapingprocess; however, as vulcanization proceeded, a firm bond between thechloroprene polymer and the rubber base stock was produced. At the endof fifteen minutes, the composite article was stripped from the mold,the chloroprene polymer being firmly bonded to the base stock and havingsubstantially no adhesion to the mold face.

When this solution of veneering composition was sprayed on to the mold,so as to give a coating of veneering composition having a thickness of0.005 inch, the film dried out in seconds. On the other hand, when suchsolution was painted on to the base stock at 82 F. to give a veneeringcomposition of 0.005 inch thickness, 24 hours were required for the fihnto dry out.

EXAMPLE II Example I was repeated using an aqueous dispersion ofchloroprene polymers, prepared ac- 6 cording to U. S. Patent 2,264,173and compounded in the following manner, as a source of the veneeringelastomer:

lauryl and myristyl derivatives.

The base stock used was identical with that used in Example I. Asatisfactory composite ar ticle Was produced.

EXAMPLE III Example I was repeated, using a co-polymer compound ofbutadiene and acrylic nitrile of the following composition as a sourceof the veneering elastomer:

Butadiene "(co-polymerized) 60.0 Acrylic nitrile (co-polymerized) 40.0Blane Fixe 40.0 Zinc oxide 5.0 Stearic acid 1.0 Benzothiazyl disulfide1.5 Sulfur 1.5 Methyl ethyl ketone 640.0 Dibutyl phthalate 15.0

The base stock used was identical with that used in Example I. Asatisfactory composite article was produced.

EXAMPLE IV Butadiene (co-polymerized) Q 60.0 Acrylic nitrile(co-polymerized) 40.0 Zinc oxide 2.0 Sulfur 1.5Phenyl-alpha-naphthylamine 1.0 Sodium dibutyl dithiocarbamate 0.5

Water 300.0

The results obtained were comparable with those of Example II.

EXAMPLE V Example IV was repeated using natural latex as a source of theveneering elastomer. It was compounded in the following manner:

Rubber latex 1 100.0

Zinc oxide 2.0 Sulfur 1.5 Phenyl-alpha-naphthylamine 1.0 Sodium dibutyldithiocarbamate 0.5

A satisfactory composite article was obtained.

EXAMPLE VI Polyvinyl acetate 50.0 Methyl alcohol 50.0 Dibutyl phthalate10.0

A satisfactory composite article was obtained.

E A iLE This experiment describes the: application of;

Pale crepe 100.0. Zinc, oxide 5.0- Channel black 2.0. Whiting 30.00Stearic acid 5.0 Petrolatum 5.0 Penyl-alpha-naphthylamine 1.5; e r t lwh i ie rmen sl l de .8 Sulfur 3.5; Diazo-amino-benzene 2;0

A satisfactory composite article. was obtained.

EXAMPLE -VIII For some time the aircraft industryhasbeen. demanding asynthetic elastomer with two ,maiorv qualifications:

resistance. Unfortunately, these two properties.

are inversely correlated as' far as present know-n- Base stoc7cElastomer A 1 100.0 Extra light calcined magnesia; 5.0 Petrolatum 2 .0Channel black 30.0 Clay 60.0 Dibutyl phthalate 10.0 Sulfur 1.0 Zincoxide p 5.0 Ph n ralpha-n ph ylamin 2 Veneer I 1 Elastomer B 2 n 90.0Elastomer C 3 10. Extra light calcined magnesia 15.0 Sulfur 0.5 Zincoxide 5.0 Phenyl-alpha-naphthylamine i 2.0 Toluene 400.0

Veneer II;

Thiokol FA? 4 100.0 Zinc oxide 10.0 Soft carbon. black 80.0 Stearic.acid 0.5 Benzothiazyl disulfide 0.3 Diphenyl guanidine 0.1 Ethylenedichloride 800.0

1 This is a freeze resistant elastic polymer of chloroprene.

2 This is a solvent resistant elastic polymer of chloroprene.

1 This is an abrasion resistant elastic polymer of chloroprene.

4 This is an oil resisting elastomer ap ea'ring on the market under thetrade name "Thiokol FAf. and to t e best of my knowledge is apolyalkylene polysulfide, obtained by the reaction of an alkali metalpolysulfi do on an alkylene dichloride, bu t its exact chemical censure:tion is unknown to me.

A portion of the base stock was molded and. cured for minutes at 90pounds stearnpressurer In separate experiments, eachof the .veneeringcompositions were painted on to hot molds in an amountsuificientto-give-a veneer 0.001 inch (1) oil resistance and (2).freezethick, the.veneering.coatings dried out, portions of thebaserstock. placed in the molds andextended into. the coated cavity. andthe whole vulcanized. Theresulting products were immersed in-.a..highoctane aircraft. gasoline'for varying periodsofztime. In the followingtable is given the linear-swell ofvtheseproducts after being immersedin. such gasoline for one day andfor 4 days; respectively.

Increase 4 days Per cent 1 Contraction of sample due to evaporation ofgasoline from surface.

Due to the characteristics of the basestock, these products were freezeresistant. The application-of VeneerII to such base-stock gave: theproperty of oil resistance to such product. The amount of the veneer wasinsufficient to materiallyaffect the freeze resistance of the product.

Valuable products are also obtained, employing-a rubber composition asthe base stock and Veneer II as the veneering composition.

It will be understood that the above examples and the specificembodiments hereinbefore given are given for illustrative purposes onlyand hence that my invention is not to be restricted to such specificembodiments, but I intend to cover my invention broadly as in theappended claims. It willbe readily apparent to those skilled in the artthat many variations and modifications can be made without departingfrom the spirit or scope of. my invention. The temperatures, volatileliquids and ingredients in the compositions may be widely varied. Also,other elastomers may be substituted for those specifically mentionedabove, both in the veneering, compositions and inthe base stocks.

I particularly intend. to include within the scope of my inventionelastomers within the ,following groups:

1. Elastoprenes I 2. Elastothiomers This class comprises primarily thepolyalkylene sulfides, such asare obtained by the reaction of alkalimetal polysulfides-onorganic compounds containing2 or more replaceablechlorine atoms on different .carbonatoms.

3. Elastoplastics This class comprises the polyvinyl. acetates;polymers, co-polymers .and inter-polymers of acrylic esters;inter-polymers and co-polymers of butadienes with various polymers ofacrylic and styrene natureimixed glyptals; plasticized polyvinylhalides; polyvinyl esters; polystyrene; and co-polymers andinter-polymers of .styrene with otherelastoplastics.

These elas'toplastics.

are quite satisfactory. A 50% solution by weight of polyvinyl acetate inmethanol, plasticized with 20 parts of dibutyl phthalate gave asatisfactory veneer when sprayed into a mold.

The process and products of my invention have many advantages overveneered products obtained by the laminating process and over suchprocess. By my process, veneered products, having a veneer of only from0.001 inch to 0.020 inch in thickness, can be made, Whereas, in thelamihating process the veneers must be above 0.030 inch in thickness.Thus, my invention makes it possible to produce" veneered products in aprac tical and economical range. By my process, the products have aveneer of constant gauge over the entire surface, whereas, such productscannot be obtained by the laminating process due to the thinning out ofthe veneer during molding. Furthermore, my process requires considerablyless time and labor than the laminating process and is much moreeconomical. By my process, a smooth surface is first produced on themold and, as a r esult, the base stock flows smoothly during the moldingoperation so that the final product is free of roughnesses, cracks andother surface imperfections. My process is applicable to the preparationof products of intricate design which could not be made by methodspreviously employed. I v

My process and the products thereof have similar advantages over thepreviously proposed process of coating the base stok with a solution ordispersion of the veneering material. For eX- ample, the products of myinvention have a veneer of more uniform gauge, the time for drying theveneer is enormously shortened, the problem of handling sticky stocks iseliminated and articles or more intricate design can be obtained.

From the above, it will be apparent that bymy invention, I have made itpossible for manufac turers to produce articles of greatly improvedphysical properties at a comparatively small expense. Furthermore, by myinvention, it is possible to produce such articles with less labor anddifliculty and in a greatly shortened period of time. It will thus beapparent that, by my invention, I have made a very valuable contributionto the art.

- I claim:

1. The process of veneering elastomers which comprises applying to thesurface of a hot mold a coating of a vulcanizable veneering elastomercomposition in an inert volatile liquid, drying the coating, placing inthe coated mold a mass of a diiTerent vulcanizable elastomercomposition, applying pressure to force such mass to conform to the moldand then vulcanizing the compositions in the mold.

2. The process of veneering elastomers which comprises applying to thesurface of a hot mold a coating of a vulcanizable synthetic veneeringelastomer composition in an inert volatile liquid, drying the coating,placing in the coated mold a mass of a different vulcanizable elastomercon position, applying pressure to force such mass to conform to themold and then vulcanizing the positions in the mold.

3. The process of veneering elastomers Which comprises applying to thesurface of a hot mold. a coating of a vulcanizable veneering elastomercomposition in an inert volatile liquid, the veneering elastomer being achloroprene polymer. drying the coating, placing in the coated mold amass of a different vulcanizable elastomer composition, applyingpressure to force. such mass 10 to conform to the mold and thenvulcanizing the compositions in the mold,

4. The process of veneering elastomers which comprises applying to thesurface of a hot mold a coating of a vulcanizable veneering elastomercomposition in an inert volatile liquid, the veneering elastomer being achloroprene polymer, drying the coating, placing in the coated mold amass of a vulcanizable rubber composition, applying pressure to forcesuch mass to conform to the mold and then vulcanizing the compositionsin the mold.

5. The process of veneering elastomers which comprises applying to thesurface of a hot mold a coating of a vulcanizable veneering elastomercomposition in an inert volatile liquid, the veneering elastomer being aco-polymer of butadiene and acrylic nitrile, drying the coating, placingin the coated mold a mass of a difierent vulcanizable elastomercomposition, applying pressure to force such mass to conform to the moldand then vulcanizing the compositions in the mold.

6. The process of veneering elastomers which comprises applying to thesurface of a hot mold a coating of a vulcanizable veneerlng elastomercomposition in an inert volatile liquid, the veneering elastomer being apolyalkylene polysulfide, drying the coating, placing in the coated molda mass of a difierent vulcanizable elastomer composition, applyingpressure to force such mass to conform to the mold and then vulcanizingthe com-positions in the mold.

'7. The process of veneering elastomers which comprises applying to thesurface of a hot mold a coating of a vulcanizable veneering elastomercomposition in an inert volatile liquid, drying the coating, placing inthe coated mold a mass of a difierent vulcanizable elastomercomposition, the elastomer of such mass being a synthetic elastomer,applying pressure to force such mass to conform to the mold and thenvulcanizing the compositions in the mold.

8. The process of veneering elastomers which comprises applying to thesurface of a hot mold a coating of a vulcanizable veneering elastomercomposition in an inert volatile liquid, the veneering elastomer being apolyalkylene polysulfide, drying the coating, placing in the coated molda mass of a diiferent vuloanizable elastomer composition, the elastomerof such mass being a synthetic elastomer, applying pressure to forcesuch mass to conform to the mold and then vulcanizing the compositionsin the mold.

9. The process of veneering elastomers which comprises applyin to thesurface of a hot mold a coating of a vulcanizable veneering elastomercomposition in an inert volatile liquid, the veneering elastomer being apolyalkylene polysulfide, drying the coating, placing in the coated molda mass of a different vulcanizable elastomer composition, the elastomerof such mass being a chloroprene polymer, applying pressure to forcesuch mass to conform to the mold and then vulcanizing the compositionsin the mold.

10. A method of making a mold-vulcanized cellular article of rubberymaterial having an 1mpervious protective skin coating of rubberymaterial; which method comprises preheating a mold to a temperature highenough to flash evaporate water; applying to the preheated mold anaqueous dispersion of a vulcanizalble rubbery composition adapted, afterdrying and vulcan1 zation, to produce an impervious protective skincoating of rubbery material, and flash-drying 11 the dispersion on themold; placing in the mold in contact with the dried coatinglayerpwhileit is still hot and before the coating has lost its tackiness fromcooling 'and contact with :the air, an unblown rubbery compositionadapted, after heating, toproduce-a cellular body portion;=andsubjecting the assembly .to molding temperature and'pressure to blowthe-unblown rubberycomposition and to vulcan'ize the coating iayer randthe-blown cellular body portion in mutual contact so as to form anintegral article; saidoperations being performed without =permittingthemold to become'cool.

11. A method of making 1a mold-vulcanized cellular article of rubberymaterial having an impervious-protective skin coating ofiarubberymaterial of substantially different composition than the cellularportion thereof; whichmethod comprises preheating a mold to atemperature high enough to flash-evaporate water; applying to-thepreheated'mold anaqueous dispersionof a vulcanizable rubbery compositionadapted, after drying and vulcanization, to produce an imperviousprotective skin coating ofr'a light-resistant rubberymaterial, and flash'dryingithe dispersion on the mold; placing in themold in "contact withthedried coating layer, while it is still hotiand "before the coatinghas .lost its :tackinessifrom cooling and contact with the air, an:unblown rubbery composition adapted, after heating, to produceacellular body portion of less light-resistant but moreresilientrulrbery material; :and subjecting the assembly :to moldingtemperature and, pressure to blow the unblown rubbery composition and tovulcanize the coating layer and the blown cellular body portion in:mutual contact so as to form an integral :article; :said-nper- =ationsbeing performed without permitting {the mold to becomecool.

12. A method of making .a mold-vulcanized cellular article of rubberymaterial having afie lular body and an impervious .pmtectiye ign coatingthereon; which method comprises ;pr;eheatingamold to aitemperaturelhighenough to hash-evaporate water; applyingto the preheated mold an aqueousdispersion of 1a neoprene composition adapted, :after drying andvulcanization, to produce an impervious protective skin coating ofzrubbery neoprene material, and flash-drying the dispersion .on 'the,mold; placing in the mold in contact with the dried coating layer,while ;it :is .still :hot and .before the coating has lcstits tackinessfrom cooling and contac with the *air, an-unblown natural rubbercomposition adapted, after heating, to produce a cellular body portion;and subjecting the assembly to molding temperature and pressure to blowthe unblown rubbery composition and to vulcanize the coating layer andthe blown cellular bodyportion in mutualcontactso asto form an integralarticle; said operations being performed without peromitting the mold tobecome cool,

,ELDEN EARL LEACH, JR.

REFERENCES CITED UNISIZED STATES PATENTs Number .Name Date 1,4355%Johnston Nov. 14, 1922 1,484,731 Malm Feb. 26, 1924:-'--'.-r""-V--:-:--- 1139423340 s heppard et al. Jan. 9, 1934 1;9:13,439 lioplginson Jan. 16, 1934 1950336 Williams Mar. 13, 1934 125949914Batricli Aug. 4, 1936 2,193,995 schelhammer Sept. 20, 1938 2;2 0 1,2 '71 gPartridgenn n n May 21, 1940 2,227,991 Winkelmann etal. Jan. 7, 1941598,324 St berger 'Jan. 19, 1943 3,315,985 -Brads haw Mar. 16, 19432,339,547 Garter Jan. 18, 19,44

' FOREIGN PATENTS v Number Country Date 4865M Great gBritain June 8 1938Certificate of Correction Patent No. 2,437,855. March 16, 1948. ELDENEARL LEAGH, JR.

It is hereby certified that errors appear in the printed specificationof the above numbered patent requiring correction as follows: Column 7,line 20, Example VII, for "Penyl-alpha-naphthylamine" readPhenyl-alpha-naphthylamine; column 12, line 28, list of referencescited, name of patentee, for Johnston read Johnston at al.; line 35, forthe patent number 2,103,905 read 2,130,905; and that the said LettersPatent should be read with these corrections therein that the same mayconform to the record of the case in the Patent Office.

Signed and sealed this 18th day of May, A. D. 1948.

THOMAS F. MURPHY,

Assistant Uowwnissianer of Patents,

